This invention relates to perfluoroalkyl halides and derivatives thereof, and to the preparation and use of such halides and derivatives.
Fluorocarbon derivatives (sometimes called organofluorine compounds or fluorochemicals) are a class of substances containing portions which are fluorocarbon in nature, e.g. hydrophobic, oleophobic, and chemically inert, and portions which are organic or hydrocarbon in nature, e.g. chemically reactive in organic reactions. The class includes some substances which are familiar to the general public, such as those which give oil and water repellency and stain and soil resistance to textiles, e.g. Scotchgard(trademark) carpet protector. Other substances of the class have various industrial uses, such as reducing the surface tension of liquids, reducing evaporation and flammability of volatile organic liquids, and improving the leveling of organic polymer coatings. Examples of industrial substances are the Fluorad(trademark) fluorochemical surfactants described in 3M Company trade bulletin 98-0211-2213-4 (38.3) BPH, issued March, 1988.
Conventional fluorochemicals can be prepared from precursors such as fluoroalkyl iodides, fluoroalkyl carboxylic acid fluorides, and fluoroalkyl sulfonyl fluorides. See for example, xe2x80x9cOrganofluorine Chemicals and Their Industrial Applicationsxe2x80x9d, R. E. Banks, Ed., Ellis Horwood, Ltd., Chichester, England, 1979, pp. 214-234.
Some perfluoroalkyl iodides can be prepared by telomerization of C2F5I or (CF3)2CFI with C2F4 yielding C2F5(C2F4)nI or (CF3)2CF(CF2CF2)nI, respectively, where n is typically from 1 to 4. See R. E. Banks, supra. All of the perfluoroalkyl iodides obtained from (CF3)2CFI contain perfluoroalkyl groups with a terminal branch, and such branched-chain perfluoroalkyl groups will hereinafter be represented by xe2x80x9cRfbxe2x80x9d. All of the perfluoroalkyl iodides obtained from C2F5I contain straight-chain perfluoroalkyl groups without branches, and such straight-chain (or xe2x80x9clinearxe2x80x9d) perfluoroalkyl groups will hereinafter be represented by xe2x80x9cRfsxe2x80x9d. For brevity, xe2x80x9cRfxe2x80x9d will hereinafter be used to represent a perfluoroalkyl group with either a straight or a branched-chain. Perfluoroalkyl iodides can be converted into other functional (or reactive) materials, for example by the following illustrative schemes.
Rfxe2x80x94I+CH2xe2x95x90CH2xe2x86x92Rfxe2x80x94CH2CH2xe2x80x94I
Rfxe2x80x94CH2CH2xe2x80x94I+H2Oxe2x86x92RfCH2CH2xe2x80x94OH
Rfxe2x80x94CH2CH2xe2x80x94I+H2NC(S)NH2xe2x86x92Rfxe2x80x94CH2CH2xe2x80x94SH
Rfxe2x80x94CH2CH2xe2x80x94Ixe2x86x92Rfxe2x80x94CHxe2x95x90CH2
The alcohol, thiol, and olefin derivatives of the above schemes can be further converted to a great variety of derivatives, e.g., acrylates and polymers thereof, sulfates and salts thereof, carboxylic acids and esters thereof, etc. These further derivatives retain the original structure of the Rf group, that is, the Rf group remains either straight or branched.
Functional materials derived from telomer iodides will (as stated above) contain either 100% straight-chain (Rfs) or 100% branched-chain (Rfb) perfluoroalkyl groups. Contradictory data have been reported in the literature regarding the relative advantage of straight-chain versus branched-chain perfluoroalkyl groups. In U.S. Pat. No. 4,127,711 (Lore et al.) perfluoroalkyl straight-chains are said to be preferred for textile applications, whereas in U.S. Pat. No. 3,525,758 (Katsushima et al.) it is disclosed that surfactants containing 100% branched-chain perfluoroalkyl groups are more effective than surfactants containing straight-chain perfluoroalkyl groups in lowering the surface tension of aqueous solutions. However, it has generally been accepted that among fluorinated surfactants of the same carbon number, straight-chain products generally give lower surface tension in aqueous solutions. Banks, supra at 222-223, describes that, except at very low concentrations (less than 0.01% or 100 ppm), lower surface tension is attained with straight-chain fluorochemicals. Additionally, an article written by Bennett and Zismann (J. Phys. Chem., 71, 1967, p. 2075-2082) discloses that a condensed monolayer of a fully fluorinated straight-chain alkanoic acid has a lower critical surface energy than its terminally branched analogue with the same chain length.
In addition to the telomerization procedure described above, another method of producing many fluorochemicals or their precursors is the fluorination process commercialized initially in the 1950s by 3M Company, which comprises passing an electric current through a mixture of the organic starting compound and liquid anhydrous hydrogen fluoride. This fluorination process is commonly referred to as xe2x80x9celectrochemical fluorinationxe2x80x9d or xe2x80x9cECFxe2x80x9d. Some early patents describing such technology include U.S. Pat. No. 2,519,983 (Simons), U.S. Pat. No. 2,567,011 (Diesslin et al.), U.S. Pat. No. 2,666,797 (Husted et al.), U.S. Pat. No. 2,691,043 (Husted et al.), and U.S. Pat. No. 2,732,398 (Brice et al.); they describe the preparation of such fluorochemical compounds as perfluoroalkyl carbonyl fluorides, e.g. C4F9xe2x80x94COF, and perfluoroalkyl sulfonyl fluorides, e.g. C4F9xe2x80x94SO2F, and derivatives thereof
When perfluoroalkyl carbonyl fluorides and perfluoroalkyl sulfonyl fluorides are prepared by electrochemical fluorination (ECF) of appropriate hydrocarbon precursors, the resulting products are mixtures of compounds, where some of said compounds contain a straight-chain perfluoroalkyl group, e.g., Rfsxe2x80x94SO2F, and others of said compounds contain a branched-chain perfluoroalkyl group, e.g., Rfbxe2x80x94SO2F. Such mixtures of compounds result even when the starting materials contain only compounds with straight-chain alkyl groups. Such mixtures of compounds, e.g. a mixture of Rfsxe2x80x94SO2F and Rfbxe2x80x94SO2F, can be represented, for brevity, by the formula, Rfsbxe2x80x94SO2F, which formula represents a mixture of compounds. The xe2x80x9csbxe2x80x9d subscripts indicate that the formula represents a mixture of compounds, that is, a mixture of Rfsxe2x80x94SO2F and Rfbxe2x80x94SO2F.
ECF-derived acid fluorides can be converted into other functional materials, for example by the following illustrative schemes.
Each Rfsb containing formula, e.g., Rfsbxe2x80x94COF, represents ECF derived mixtures which contain some compounds with a straight-chain perfluoroalkyl group and other compounds with a branched-chain perfluoroalkyl group.
U.S. Pat. No. 2,950,317 (Brown et al) describes a process for the preparation of fluorocarbon sulfonyl chlorides from the corresponding fluorocarbon sulfonyl fluorides.
An article by Park et al. (23, J. Org. Chem, 1166-1169 (1958)) describes the preparation of certain fluorochemical compounds with three or less fully-fluorinated carbon atoms. Compounds described include n-C3F7xe2x80x94CH2CH2xe2x80x94I and n-C3F7xe2x80x94CH2xe2x88x92CO2H.
Briefly, the present invention, in one aspect, provides novel fluorochemical compositions which comprise a mixture of perfluoroalkyl halide compounds. Some of the perfluoroalkyl halide compounds of the mixture contain a straight-chain group (the term xe2x80x9cstraight-chainxe2x80x9d is used herein in its accepted sense to mean normal or unbranched perfluoroalkyl group, e.g., CF3CF2CF2CF2xe2x80x94), and some contain a branched-chain perfluoroalkyl group (e.g., (CF3)2CFCF2xe2x80x94).
The perfluoroalkyl halide compounds comprise a perfluoroalkyl group, a halogen atom selected from the group consisting of Cl, Br, and I, and a fluorine-free alkylene linking group bonded to the perfluoroalkyl group and to the halogen atom. The alkylene linking group contains at least two catenary carbon atoms, one of which is bonded to the perfluoroalkyl group, and the other of which is bonded to the halogen atom (e.g., as in Rfsbxe2x80x94CH2CH2xe2x80x94I, but not as in Rfsbxe2x80x94CH(CH3)xe2x80x94I). The carbon atom of the alkylene linking group which is directly bonded to the perfluoroalkyl group will be referred to as the alpha carbon atom, and the catenary carbon atom of the alkylene linking group which is bonded to said alpha carbon atom will be referred to as the xe2x80x9cbeta carbon atomxe2x80x9d. Such xcex1 and xcex2 carbon atoms are illustrated, for example, in the formula 
In another aspect, this invention provides novel fluorochemical compositions which comprise a mixture of perfluoroalkyl derivative compounds of said perfluoroalkyl halide compounds. Some of said perfluoroalkyl derivative compounds of said mixture contain a straight-chain perfluoroalkyl group, e.g., CF3CF2CF2CF2xe2x80x94, and some contain a branched-chain perfluoroalkyl group, e.g., (CF3)2CFCF2xe2x80x94. Said derivatives are obtained from said halides by one or more steps, and retain from the precursor halides the perfluoroalkyl group and the alpha and beta carbon atoms of the linking group. One or both of said alpha and beta carbon atoms may be converted, for example, to a carbonyl (Cxe2x95x90O) or alkenylene carbon atom (Cxe2x95x90C), but they are always retained in some form in the derivative.
Preferably, the compositions of this invention comprise a mixture of compounds wherein 50 to 95% of said compounds contain a straight-chain perfluoroalkyl group (Rfs), and wherein 5 to 50% of said compounds contain a branched-chain perfluoroalkyl group (Rfb). Most preferably, the compositions of this invention comprise a mixture of compounds wherein 60 to 90% of said compounds contain a straight-chain perfluoroalkyl group (Rfs) and wherein 10 to 40% of said compounds contain a branched-chain perfluoroalkyl group (Rfb).
The compositions of this invention also may contain mixtures of compounds such that the number of carbon atoms in the perfluoroalkyl groups are predominately, e.g., greater then 70%, of one length, for example where greater then 70% of all perfluoroalkyl groups in the mixture of compounds have 8 carbon atoms.
Because of the wide variety of the fluorochemical compositions of this invention, they can be used in numerous applications, including those where conventional fluorochemicals are used. Such applications are described, for example, in Banks, supra, which descriptions are incorporated herein. The fluorochemical compositions of this invention are useful in improving or imparting properties to solutions and substrates such as wetting, penetration, spreading, leveling, foaming, foam stabilization, flow properties, emulsification, dispersability, and oil, water, and soil repellency.
A class of the fluorochemical compositions of this invention comprises a mixture of perfluoroalkyl halide compounds which mixture can be represented by Formula I.
Rfsbxe2x80x94CH2CH(R1)R2xe2x80x94Xxe2x80x83xe2x80x83I.
In Formula I, the xe2x80x9cfsbxe2x80x9d subscript is meant to indicate that Formula I represents a mixture of compounds, that is, a mixture of Rfsxe2x80x94CH2CH(R1)R2xe2x80x94X and Rfbxe2x80x94CH2CH(R1)R2xe2x80x94X. Some of said compounds contain a straight-chain perfluoroalkyl group (Rfs) and all others of said compounds contain a branched-chain perfluoroalkyl group (Rfb).
In Formula I, Rfsb is a perfluoroalkyl group. Said perfluoroalkyl group is saturated, mono-valent, and has at least 4 fully-fluorinated carbon atoms. While the perfluoroalkyl group can contain a large number of carbon atoms, compounds where the perfluoroalkyl group is not more than 20 carbon atoms will be adequate and preferred since larger radicals usually represent a less efficient utilization of the fluorine (lower fluorine efficiency) than is obtained with shorter chains. Perfluoroalkyl groups containing from about 4 to about 10 carbon atoms are most preferred.
In Formula I, R1 is a lower alkyl group, e.g., with 1 to 4 carbon atoms, or an aromatic group, e.g., phenyl, or combinations thereof, e.g., tolyl. R1 may also contain hetero atoms, e.g., S, O, N, Si, for example R1 may be xe2x80x94CH2xe2x80x94OH.
In Formula I, R2 is a covalent bond or an alkylene group such as (CH2)m, where m is from 1 to 20, or xe2x80x94CH(R) where R is as defined for R1, and R2 may also contain said hetero atoms.
In Formula I, the carbon atom bonded to the perfluoroalkyl group may be referred to as the alpha carbon atom and is represented in Formula I as the xe2x80x9cCxe2x80x9d in CH2. The other depicted carbon atom, which is bonded to the alpha carbon atom, may be referred to as the beta carbon atom and is represented in Formula I as the xe2x80x9cCxe2x80x9d in CH(R1).
In Formula I, X is I, Cl, or Br.
A subclass of the fluorochemical compositions of this invention comprises a mixture of perfluoroalkyl halide compounds which mixture can be represented by Formula II.
Rfsbxe2x80x94(CH2CH2)nxe2x80x94Xxe2x80x83xe2x80x83II
In Formula II, Rfsb and X are as described above for Formula I and n is an integer from 1 to 5.
The perfluoroalkyl halide mixtures of this invention are reactive chemicals and can be converted into their reactive or functional derivatives by one or more steps. A class of such derivatives can be represented by the formula Rfsbxe2x80x94Z where Rfsb is as defined and described above and Z is an organic moiety or an oxygen-containing inorganic moiety that is a one-step or multi-step derivative of the halide compounds. Various functional embodiments of Z make the derivatives useful reagents for the introduction of the Rfsb moiety into molecules. Z can be an organic functional moiety, i.e., one which contains one or more carbon atoms, such as carbonyl-containing, sulfonyl-containing, alkylene-containing, nitrogen-containing, and oxygen-containing moieties or Z can be an oxygen-containing inorganic moiety, such as sulfonyl-containing and sulfonyloxy-containing moieties. Representative functional Z moieties are, for example, polymerizable groups which will undergo electrophilic, nucleophilic, or free radical reaction, derivatives with such groups being useful to form polymers comprising polymeric chains having a plurality of pendant perfluroalkyl groups. Derivative compounds of this invention include carboxylic and sulfonic acids and their metal and ammonium salts, esters, including alkyl and alkenyl esters, amides, tetrahydroalcohols (xe2x80x94C2H4OH), esters of tetrahydro-alcohols, acrylates (and polyacrylates), mercaptans, alkenyl ethers, etc. Stated otherwise, Z in the above formulas can contain xe2x80x94COOH, xe2x80x94COOM1/v, xe2x80x94COONH4, xe2x80x94CH2COOR, xe2x80x94CONH2, xe2x80x94COONR1R2, xe2x80x94NR1R2, xe2x80x94CONR1R3A, xe2x80x94CH2OH, 
xe2x80x94SO3M1/v, xe2x80x94SO3NH4, xe2x80x94SO2NR1R2, xe2x80x94SO2NR1R3A, xe2x80x94SO2NH2, xe2x80x94SO3R, xe2x80x94CH2SH, xe2x80x94CH2NR1R2, xe2x80x94CH2OCOCR4xe2x95x90CH2, CH2OCOCF2SF5, and the like, where M is a metal atom having a valence xe2x80x9cvxe2x80x9d, such as a monovalent metal atom like K or Na; R is alkyl (e.g. with 1 to 14 carbon atoms), aryl (e.g. with 6 to 10 or 12 ring carbon atoms), or a combination thereof (e.g. alkaryl or aralkyl); R1 and R2 are each independently H or R; R3 is alkylene (e.g. with 1 to 13 carbon atoms; R4 is H or CH3; A is an aliphatic or aromatic moiety, which can contain a carboxy or sulfo group or an alkali metal or ammonium salt or ester thereof, a carboxamido, a sulfonamido, or contain 1 to 3 hydroxy groups, 1 or more ether-oxygen or oxirane-oxygen atoms, a cyano group, a phosphono group, or one or more primary, secondary, or tertiary amine groups, or quaternized amine group, or other functional group.
The above illustrated derivatives can be converted to other derivative fluorochemical compositions of this invention. For example, hydroxy functional derivatives can be converted to corresponding sulfate derivatives useful as surfactants as described, for example, in U.S. Pat. No. 2,803,656 (Ahlbrecht et al.) or phosphate derivatives useful as textile and leather treating agents as described, for example, in U.S. Pat. No. 3,094,547 (Heine). Hydroxy functional derivatives can also be reacted with isocyanates to make carbamato-containing derivatives such as urethanes, carbodiimides, biurets, allophanates, and quanidines useful in treating fibrous substrates such as textiles as described, for example, in U.S. Pat. Nos. 3,398,182 (Guenthner et al.), U.S. Pat. No. 4,024,178 (Landucci), U.S. Pat. No 4,668,406 (Chang), U.S. Pat. No. 4,606,737 (Stern), and U.S. Pat. No. 4,540,497 (Chang et al.), respectively.
Amine functional derivatives can be converted to corresponding amine salts useful as surfactants, as described, for example, in U.S. Pat. Nos. 2,764,602 (Ahlbrecht), U.S. Pat. No. 2,759,019 (Brown et al.) or amphoteric surfactants as described, for example, in U.S. Pat. No. 4,484,990 (Bultman et al.). Amine functional derivative can be successively reacted to form an amphoteric surfactant as described, for example, in U.S. Pat. No. 4,359,096 (Berger) (see Table I thereof).
The polymerizable functional derivatives of this invention can be used to make polymers such as polyacrylates, polyesters, polyurethanes, polyamides, and polyvinyl ethers. Such polymers can be made by conventional step-growth, chain-growth, or graft polymerization techniques or processes. The step-growth polymers can be made, for example, from those derivatives having hydroxyl, carboxyl, isocyanato, or amino polymerizable groups. The acrylate, methacrylate, or vinyl derivatives of this invention can be used to make chain-growth polymers, such as polyacrylates. Fluorochemical ethylenically unsaturated monomers of this invention can be homopolymerized to make homopolymers, or copolymerized with copolymerizable monomers to make random, alternating, block, and graft polymers. Copolymerizable monomers which can be used include fluorine-containing and fluorine-free (or hydrocarbon) monomers, such as methyl methacrylate, ethyl acrylate, butyl acrylate, octadecylmethacrylate, acrylate and methacrylate esters of poly(oxyalkylene) polyol oligomers and polymers, e.g., poly(oxyethylene) glycol dimethacrylate, glycidyl methacrylate, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, vinylidene fluoride, acrylonitrile, vinyl chloroacetate, isoprene, chloroprene, styrene, butadiene, vinylpyridine, vinyl alkyl ethers, vinyl alkyl ketones, acrylic and methacrylic acid, 2-hydroxyethyl acrylate, N-methylolacrylamide, 2-(N,N,N-trimethylammonium)ethyl methacrylate and the like.
The polymers can be applied in the form of an aqueous or non-aqueous solution or emulsion as a coating or finish to modify the free surface energy of a substrate, e.g. a non-porous substrate such as glass, metal, plastic, and ceramic or a fibrous or porous substrate such as textile, e.g., nylon carpet fiber or polyester outerwear fabrics, leather, paper, paperboard, and wood to impart oil and water repellency thereto, as described, for example, in the Banks reference supra.
The relative amounts of various comonomers which can be used with the monomers of this invention generally will be selected empirically and will depend on the substrate to be treated, the properties desired from the fluorochemical treatment, e.g., the degree of oil and/or water repellency desired, and the mode of application to the substrate. Generally, in the case of copolymers, of the interpolymerized or repeating units in the polymer chain, 5 to 95 mole percent of such units will contain pendant perfluoroalkyl groups. The fluoroaliphatic polymers of this invention can be blended with other or known polymers, such as perfluoromethyl-terminated fluoroaliphatic vinyl polymers, and the blend used to modify surface properties, e.g. of textiles such as fabrics to provide them with improved properties such as oil and water repellancy.
Fluorochemicals of this invention which are useful as surfactants generally are those having a polar group such as xe2x80x94CO2Na, xe2x80x94SO2NHC3H6N+(CH3)3Clxe2x88x92, xe2x80x94SO2N(C2H5)C2H4O(C2H4O)7H, and xe2x80x94CONHC3H6N+(CH3)2CH2CO2xe2x88x92, these moieties being representative of the polar groups in anionic, cationic, non-ionic, and amphoteric surfactants, respectively. The surfactants are useful in improving or imparting properties to aqueous and non-aqueous (organic) liquid systems such as wetting, penetration, spreading, leveling, foaming, foam stabilization, flow properties, emulsification, dispersability, and oil, water, and soil repellency. Said liquid system generally will comprise a liquid phase (in which the surfactant will be dissolved or dispersed) and one or more other phases selected from the group consisting of another liquid phase, a gas phase, and a phase of dispersed solids (e.g. polymer solids), and the system can be in the form of an emulsion, suspension, or foam (such as an air foam). Examples of such liquid systems, or application areas for said surfactants, include rinsing, cleaning, etching, and plating baths, floor polish emulsions, photographic processes, water base coatings, powder coatings, solvent based coatings, alkaline cleaners, fluoropolymer emulsions, soldering systems, and specialty inks, such as described, for example, in 3M Bulletin 98-0211-2213-4 (38.3) BPH.
The fluorochemicals useful as surfactants also can be incorporated into or mixed with other substances. For example, if sufficiently thermally stable, they can be incorporated into polymeric materials, such as polyamides, e.g. nylon, or polyolefins, e.g., polypropylene, which are cast, blown, extruded, or otherwise formed into shaped articles, such as films and fibers, the so-incorporated fluorochemicals modifying the properties of the shaped articles, such as the oil and water repellency of their surfaces. The fluorochemical surfactants of this invention can also be mixed with other surfactants, such as hydrocarbon surfactants and/or the conventional fluorochemical surfactants, e.g. those disclosed in said U.S. Pat. Nos. 2,567,011 and 2,732,398, and such mixed surfactants used to form, for example, aqueous, film-forming foams as described in U.S. Pat. No. 3,562,156 (Francen).
In the following examples, it is shown that the fluorochemical compositions of this invention impart improved properties. As shown in the working examples below, some of the compositions of this invention impart improved oil repellency to textile substrates compared to fluorochemical compositions derived from ECF and containing a sulfonamido linking group. As also shown, some of the compositions of this invention provide lower surface tension to, and have better solubility in, organic or aqueous systems compared to fluorochemical compositions obtained from telomerization (compositions where all compounds have straight-chain, or where all compounds have branched-chain perfluoroalkyl groups).
A convenient route to the perfluoroalkyl halide mixtures of this invention utilizes perfluoroalkyl sulfonyl fluorides (obtained from ECF) according to the following illustrative schemes.
Rfsbxe2x88x92SO2F+Na2SO3+I2xe2x86x92Rfsbxe2x80x94I
Rfsbxe2x80x94I+C2H4xe2x86x92Rfsbxe2x80x94C2H4xe2x80x94Ixe2x80x83xe2x80x83A
Rfsbxe2x80x94SO2Fxe2x86x92Rfsbxe2x80x94SO2Cl
Rfsbxe2x80x94SO2Cl+C2H4xe2x86x92Rfsbxe2x80x94C2H4xe2x80x94Clxe2x80x83xe2x80x83B
Rfsbxe2x80x94SO2Fxe2x86x92Rfsbxe2x80x94SO2Br
Rfsbxe2x80x94SO2Br+C2H4xe2x86x92Rfsbxe2x80x94C2H4xe2x80x94Brxe2x80x83xe2x80x83C
The perfluoroalkyl halide mixtures from Schemes A, B and C are readily converted to various derivatives containing for example hydroxyl, thiol, amino, acids, acid salts, esters, etc., and adducts and derivatives thereof, e.g., urethanes, acrylates and polymers thereof, etc., using conventional synthetic procedures, many of which are described in the examples. Each perfluoroalkyl halide mixture can be converted to either of the other two perfluoroalkyl halide mixtures.